During the fighting of a fire, a firefighter works in a very hostile environment. Many firefighters lose their lives while fighting fires. Most of the deaths of firefighters while fighting fires are a result of stress, heart attacks, strokes, and the like. Of course, a firefighter must be protected from the environment within which the firefighter works.
Beyond the dangers to the firefighter's life, firefighter's are also exposed to great danger of severe burns. Their bodies are exposed to burning, smoldering or other heated surfaces or surfaces from which steam or other hot vapors emanate. This normally occurs either where firefighter's are brought into contact with such surfaces in supporting themselves on such a surface, or in moving through a burning, smoldering or heated structure. This most often has effect on the joint areas and other areas which are compressed by localized pressure, and/or dampened by heated vapors or liquids. Localized pressure can occur in these areas for instance where a firefighter kneels or crawls, leans on his or her elbows, or brings his or her shoulders into contact with a burning, smoldering or heated surface, especially those from which liquids and/or vapors emanate.
Hot liquids and vapors are particularly dangerous due to their high heat capacity and their ability to penetrate a firefighter's garment, especially where the garment is compressed by localized pressure, causing rapid and serious burning.
Localized pressure may also occur in a firefighter's garment as the firefighter moves and works. During firefighting activity, a firefighter frequently finds it necessary to carry relatively heavy and/or bulky items, such as breathing apparatus, tanks, water hose and the like; and even fire victims. Such heavy items carried by the firefighter serve to apply increased pressure upon portions of the firefighter's clothing. Compression of the firefighter's garment in these areas renders corresponding areas of the firefighter's garment more permeable to hot vapors or liquids and thus more vulnerable to burns.
Burn injury (i.e., first degree burn) occurs when skin temperatures rise above 115.degree. F. regardless of exposure time. Second degree burns or blistering occurs when skin temperatures reach about 132.degree. F. Burn injury is a function of temperature and exposure time and the rate of injury increases logarithmically with the increase in temperature. Also, total burn damage is the sum of that resulting from the heating and cooling back to a safe skin temperature level.
Very little research has been accomplished to study the effects of conduction of heat through compressed, wet fabrics. Most studies have investigated the radiative-convective thermal loads typically encountered during structural firefighting. These studies pertain to pain or burn injury on contact with metals, plastics or glass (e.g., Stoll, et al. 1979, Veghte 1974). The physical environment firefighter's contend with is one which features potentially dangerous temperature extremes. As a result, firefighting is an extremely hazardous profession.
Air temperature and thermal radiation correspond for routine, ordinary or emergency firefighting situations. Under emergency conditions encountered inside a flashover room, the function of firefighter's clothing is simply to provide 15 to 30 seconds of protection to allow escape.
One way in which heat is transferred is by conduction. Heat loss or gain by conduction normally concerns only that part of one surface which is in direct contact with another surface. Heat flows through the resulting continuity of surface. The roll of heat conduction in bunker gear is usually underestimated. It is significantly increased to protective clothing as wet or compressed. Water can provide a conductive bond between surfaces that might not otherwise touch, and can increase the heat conduction by displacing insulating air between and within the layers of clothing. Even without water, compression brings surfaces closer together, thus permitting more conduction of heat and providing less potentially insulative air between clothing layers.
Recent NFPA standards (1500 and 1971) require full torso bunker clothing protection for structural firefighter's (both coat and pants, as opposed to the coat alone with high boots worn in the past). This is required due to the tremendously high levels of protection the full torso system offers when unexpected though inevitable exposure occurs. However, there are still some disadvantages associated with this system. For instance, while the full torso system protects the firefighter much more effectively by insulating him or her from the fire, this insulation may cause the firefighter not to feel discomfort as early otherwise he or she might. Since the perception of discomfort is an indicator to the firefighter that he could be vulnerable, this remains a disadvantage. The firefighter may absorb a lot of heat energy into a system before sensing that he or she is in danger. However, experienced firefighter's eventually learn to gauge a particular situation by the degree of discomfort they feel. Nonetheless, the change in insulation can cause the firefighter not to sense the thermal loading problems he may encounter. These problems become more severe when the firefighter's garment is wet (such as through sweating or exposure to water). Once a firefighter's garment becomes wet, the warning time (i.e., the time between pain recognition and the onset of second degree burn blistering) decreases substantially. Also, when the firefighter's garment system is wet, the decreased insulative performance is exasperated by the fact that water held in the garment system, when exposed to sufficient heat, turns into steam, expanding in volume and carrying tremendous amounts of heat and energy into the most permeable parts of the garment.
For instance, when a firefighter is kneeling on a substantially impermeable surface compressing the garment system tightly against the skin at the knee, this area can present a target for hot vapors or gases which can permeate into the garment. Blistering on the knees commonly occurs when firefighter's are crawling on hot surfaces. Because of this, most firefighter's use a so called "duck walk" when hot floors are encountered. Leather knee pads have been used in the past to provide more thermal insulation and abrasion protection in this area. However, these pad did not provide means for dispersing hot fluids from the pad area. The degree of wetness, the degree of thermal loading and constriction of the garment all contribute to the extent of steam generation, and correspondingly, the extent resulting burns. Firefighter's knee burns have occurred quite often as a result. The same problem exists (although not quite as frequently) at other stressed, pinned or compressed body areas such as shoulders, elbows, shins, forearms, etc.
Present firefighter garment designs have not provided for improved protection from hot vapors and liquids. Firefighter's coats and trousers customarily have three layers of material: an outer shell or layer, which is flame resistant and abrasion resistant, an intermediate layer which is a moisture barrier, and an inner layer, which is a thermal barrier. These layers may be three separate distinct layers or may be one or two members.
Recently, firefighter's garments have been described which feature so-called "dead air" spaces are described in U.S. Pat. Nos. 4,897,886 and 5,001,783, both to Grilliot et al; and both of which are hereby incorporated herein by reference.
Accordingly, it an object of the present invention to provide a protective garment which has the same quality of protection or better protection against the environment than conventional protective garments, but which further protect the firefighter from the dangers of hot liquids or vapors. It should be understood that while some of the advantages of the protective garment of the present invention are described in terms of a firefighter's garment, the protective garment of the present invention is not limited to use in firefighting. Rather, it may be used for protection against similarly hostile environments.